Pipette tips are small, conically shaped devices that are affixed to the end of a pipetter for use in laboratory analysis. The pipetter is a mechanical device that includes a pump-type action to draw fluid up into the pipette tip in a specified amount so that the fluid can be transferred to another receptacle for the test to take place.
In recent years, the use of pipette tips has grown explosively so that they are sold in packages, usually containing about 100 tips. In one particular version, they are sold with 96 tips to a rack. This has become a common factor as pipetters are now made to handle multiple pipette tips, usually eight or twelve at a time.
Pipette tips are used only once. As indicated above, they are used in great quantities. In light of the use, ordinarily with some kind of medical or biological testing, sterility is of paramount importance. Accordingly, the racks mentioned above come fully equipped with pipette tips that have been sterilized so that the laboratory technician need not go through any particular sterilization step prior to use.
In order to save space, the purveyors of pipette tips generally sell them in nested racks. Such racks are described in U.S. Pat. No. 3,853,217 dated Dec. 10, 1974, and issued to Scordato. Stacking or nesting racks of the type described in Scordato have more recently been replaced by covered racks as represented by the covered rack of U.S. Pat. No. Des. No. 271,239, issued Nov. 1, 1983 to Lemieux et al. The Lemieux type of covered rack is shown in a variant hinged-type box, again with the normal 96 tips to the rack, but with the lower half of the box being the skirt of the Lemieux type rack.
In both the Lemieux rack and the hinged-top box described above, the surface upon which the tips are placed is of necessity reinforced to handle the incumbent force of the pipetter as it is brought down into contact with eight tips at a time. Since the fit of the tip on the pipetter is a friction fit, the top surface of the rack must, of necessity, withstand the pressure imposed by the pipetter so that either all eight or all twelve tips can be picked up at one time.
The nested racks of the Scordato era did not have the reinforcement found in the more recent racks of the '239 reference or the hinged-top boxes. The drawbacks with the Lemieux-type racks and the hinged-top boxes were that they were not nestable in the sense of Scordato and therefore considerably more volume was taken up by these racks.
The problem with nesting racks is that they are easily overturned on the laboratory bench. Thus, if there is a stack of five racks containing upwards of 100 tips per rack, the technician may very well be in the position of having lost 500 pipette tips as the sterilization is lost if the racks are overturned and the tips fall on the bench or floor. While the tips may be reracked (generally by hand), they would still require at least sterilization and, at worst, cleaning and sterilization. Due to the relatively low cost of the racks, they are generally thrown away if sterilization is lost.
In short, the problem with the existing pipette tip racks is that the stand-alone rack takes up too much space in the sale of the rack, while the nesting racks are easily overturned, with the loss of the pipette tips.
Another problem with the existing nesting racks is that when the individual rack is taken off the pile, there is no readily available cover or bottom piece in the rack and contamination can enter into the rack itself.
Accordingly, this invention is for a stacking pipette tip rack that includes an interlock between racks so that a plurality of pipette tip racks can be stacked one atop another. Also included in the invention is a cover piece and a base piece, both of which are adapted to utilize the locking mechanism of the rack. Finally, a separate hinged-top box may be provided with the plurality of racks so that a technician using a small quantity of tips can have at his or her laboratory bench the convenience of the single rack with a cover and a base or alternatively, a hinged-top box. On the other hand, the user of a large quantity of tips may be provided a plurality of tip racks that include a cover and a base member and that are interlocked so that if the stack is overturned only the tips in the top rack are in jeopardy and then only if the top is not in place.
This structure overcomes the shortcomings of the existing pipette tip racks while retaining the conventional multiple tip arrangement in the racks configured to be utilized with the multiple pipetters.